The Ocean Thermal Energy Conversion Project Uses the Surface Water $20 ^ { \circ } \mathrm { C }$

Multiple Choice

The ocean thermal energy conversion project uses the surface water near tropical islands with a temperature of $20 ^ { \circ } \mathrm { C }$ as the hot temperature reservoir, and the water at some depth, with a temperature of $5.0 ^ { \circ } \mathrm { C }$ , as the cold temperature reservoir for a heat engine. What is the maximum possible efficiency of an engine running between those two temperatures?

A) $7.9 \%$
B) $4.7 \%$
C) $30 \%$
D) $5.1 \%$
E) $15 \%$